The App

A Three Point Monte Carlo app for iPhone, Android and web.

This is a Flutter app that I am working on to learn Flutter. It is in a very rough state at the moment, but will get better. The add button adds rows for input. Hitting submit will give you a histogram of the results of running three point estimates of the set of numbers you input 20,000 times. It will be available for iPhone, Android and web.

I am curious if this would be valuable for time or money estimates such as buying a house to fix up and sell, or project time or cost, or buying a business etc. 

The more the project can be broken down into items and the better the minimum, most likely and maximum estimates are, the better the final result. One note, the minimum and maximum need to be true minimum and maximum. For the house example it would be the lowest or highest purchase price or job estimate like roof repair, plumbing, drywall etc. that would actually happen, each as a separate min, likely and max. The most likely value is just as it sounds. 

Here is a good link to understand the math of Monte Carlo simulation and three point estimates a bit better: eight2late.wordpress.com

Here is a google sheet similar to the Excel sheet in that article but simplified to not have parallel tasks to see it in a different form: google doc

And here is the web version...

Estimating the cost of purchasing a house to fix up:

There are two ways to view this curve, one is to say that if you do this 20K times, then these are the likely outcomes based on the information provided. The other way to look at it is by confidence interval. Based on how confident you need to be that the actual result will be inside your range and taking a range of numbers that represent it. If you want high confidence, then the range would be wider like 567 to 594 for this curve. Less confidence would a narrower range like 573 to 584. Even less confidence would be the 578 which is both the Mean and Median in this case. Less confidence just means that if you did it 20K times there would be more results outside your range than a wider, more confidant range.

A good book to learn about confidence intervals and how to calibrate yourself to be able to make estimates in a certain range is: [How to Measure Anything: Finding the Value of Intangibles in Business](https://www.amazon.com/How-Measure-Anything-Intangibles-Business-dp-1118539273/dp/1118539273/)

3 point mc

This is the web version of the estimation app. It is fully functional, try it out. (It doesn't show up in the summary text so you will have to click to see the full post.)

A few tips:

• If you want to add more items, hit the run button and then come back to save the current items. At the moment it doesn't automatically save them.